Polaron: Difference between revisions

The energy spectrum of an electron moving in a periodical potential of a rigid [[crystal lattice]] is called the [[Bloch spectrum]], which consists of allowed bands and forbidden bands. An electron with energy inside an allowed band moves as a free electron but has an [[effective mass (solid-state physics)|effective mass]] that differs from the electron mass in vacuum. However, a crystal lattice is deformable and displacements of atoms (ions) from their equilibrium positions are described in terms of [[phonons]]. Electrons interact with these displacements, and this interaction is known as electron-phonon coupling. One possible scenario was proposed in the seminal 1933 paper by [[Lev Landau]], which includes the production of a lattice defect such as an [[F-center]] and a trapping of the electron by this defect. A different scenario was proposed by [[Solomon Isaakovich Pekar|Solomon Pekar]] that envisions dressing the electron with lattice polarization (a cloud of virtual polar phonons). Such an electron with the accompanying deformation moves freely across the crystal, but with increased effective mass.<ref>L. D. Landau and S. I. Pekar, Effective mass of a polaron, Zh. Eksp. Teor. Fiz. '''18''', 419–423 (1948) [in Russian], English translation: Ukr. J. Phys., Special Issue, '''53''', pp.&nbsp;71–74 (2008), {{cite web |url=http://ujp.bitp.kiev.ua/files/journals/53/si/53SI15p.pdf |title=Archived copy |access-date=2016-08-10 |url-status=dead |archive-url=https://web.archive.org/web/20160305170544/http://ujp.bitp.kiev.ua/files/journals/53/si/53SI15p.pdf |archive-date=2016-03-05 }}</ref> Pekar coined for this charge carrier the term '''polaron'''.